[Intel-wired-lan] [PATCH 3/3 net-next] net_device: Add minimal padding to allow for net_device pointer alignment
Thomas Graf
tgraf at suug.ch
Thu Apr 9 23:43:28 UTC 2015
Makes use of the __alignof__ GCC builtin to determine the minimal
amount of padding required to align the pointer afterwards.
Due to use of ____cacheline_aligned_in_smp inside net_device,
struct net_device is actually always a multiple of SMP_CACHE_BYTES
so typically no padding is needed but this logic is kept in place
in case that is no longer the case.
Signed-off-by: Thomas Graf <tgraf at suug.ch>
---
include/linux/kernel.h | 2 ++
net/core/dev.c | 3 +--
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6d630d..4ec018f 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -50,6 +50,8 @@
#define __ALIGN_MASK(x, mask) __ALIGN_KERNEL_MASK((x), (mask))
#define PTR_ALIGN(p, a) ((typeof(p))ALIGN((unsigned long)(p), (a)))
#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0)
+#define PTR_ALIGN_PAD(type, a) \
+ ({ (__alignof__(type) < (a)) ? (a) - __alignof__(type) : 0; })
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
diff --git a/net/core/dev.c b/net/core/dev.c
index b2775f0..2b43aba 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6794,8 +6794,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
alloc_size = ALIGN(alloc_size, NETDEV_ALIGN);
alloc_size += sizeof_priv;
}
- /* ensure 32-byte alignment of whole construct */
- alloc_size += NETDEV_ALIGN - 1;
+ alloc_size += PTR_ALIGN_PAD(struct net_device, NETDEV_ALIGN);
p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
if (!p)
--
1.9.3
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